Hello Anand,

Why build when you can buy? There are plenty of ready made filters available from Schaffner, Epcos, Belling-Lee, Roxburgh and others, that have been approved to the highest safety standards (i.e. VDE).

If you do want to build it yourself, you will need to calculate the component values based upon the suppression you want to acheive at a certain frequency. For instance if you have a SMPS, you will want maximum suppression at the switching frequency.

Typical values are around 10mH for the common-mode inductor, between 33nF and 220nF for the parallel capacitor and between 1500pF and 4700pF for the earth capacitors. The parallell capacitor must be Class X1 or X2 and the earth capacitors must be Class Y. If the filter is intended for a medical application, the earth capacitors must be omitted.

Regards,
Rob.